How to enable NSZombie in Xcode?

Environment variables are now part of the "scheme".

To edit the scheme and turn on zombies:

• In the "Product" menu, select "Edit Scheme".

• Go to the "Run Foo.app" stage in the left panel, and the "Arguments" tab on the right.

• Add NSZombieEnabled to the "Environment Variables" section and set the value to YES, as you could in Xcode 3.

In Xcode 4.1 and above, there's also a checkbox on the "Diagnostics" tab of the "Run" stage to "Enable Zombie Objects".

With Xcode 6.4:

I encountered the same problem with troubleshooting EXC_BAD_ACCESS and had hard time to find the setting with Xcode 4.2 (the latest one that comes with iOS5 SDK). Apple keeps on moving things and the settings are no longer where they used to be.

Fortunately, I've found it and it works for the device, not just Simulator. You need to open the Product menu in the Xcode, select Edit scheme and then choose the Diagnostics tab. There you have "Enable Zombie Objects". Once selected and run in debugger will point you to the double released object! Enjoy!

In short

Product->Edit Scheme->Diagnostics-> Click Enable Zombie Objects

Product > Profile will launch Instruments and then you there should be a "Trace Template" named "Zombies". However this trace template is only available if the current build destination is the simulator - it will not be available if you have the destination set to your iOS device.

Also another thing to note is that there is no actual Zombies instrument in the instrument library. The zombies trace template actually consists of the Allocations instrument with the "Enable NSZombie detection" launch configuration set.